A receiver may be implemented in the following manner. A frequency converter converts a radio frequency signal into an intermediate frequency signal that comprises two components: an in-phase component and a quadrature component. A so-called polyphase filter filters the intermediate frequency signal so as to suppress unwanted signals. The filtered intermediate frequency signal is further processed so as to obtain information that is conveyed by the radio frequency signal.
The extent to which the polyphase filter suppresses unwanted signals depends on the relative accuracy of the components that constitute the polyphase filter. The higher the relative accuracy is, the better the unwanted signals are suppressed.
U.S. Pat. No. 4,647,843 describes a polyphase filter that consists of a ring of series connected alternate resistors and capacitors. The polyphase filter has junction points between the resistors and capacitors that alternately form inputs and outputs of the filter. The resistors are trimmed so that a product of the resistance and the capacitance of the component connected to each respective output is equal to a product RC, R and C being the nominal resistance and capacitance of the resistors and capacitors. In order to manufacture the polyphase filter at a relatively low cost, thick film techniques are used. The resistors of each network section are trimmed to the desired value after they have been formed on a thick film substrate. The resistors are trimmed using a laser in a known manner.